1. Field of the Invention
The present invention relates to techniques for the detection of human pathogens in foods. More particularly, the present invention relates to a novel method useful for the detection and differentiation of virulent and avirulent strains of the bacterium Yersinia enterocolitica "Y. enterocolitica" using a crystal violet "CV" dye binding technique.
2. Description of the Prior Art
Y. enterocolitica is a potential human pathogen which has caused considerable concern in the food industry because of its ability to grow at refrigeration temperatures. Since its discovery over 40 years ago, the microorganism has been isolated from various food products including milk, milk products, egg products, raw meats, poultry and vegetables.
Various strains of Y. enterocolitica have been isolated. However, the disease-causing potential of the microorganism is associated with the virulent plasmid-bearing "P.sup.+ " strains of enterocolitica. Consequently, the evaluation of foods as well as clinical and environmental samples for the presence of Y. enterocolitica requires the additional determination of the potential virulence of the strains isolated.
Presently, the evaluation of isolates of Y. enterocolitica requires either the use of sophisticated techniques such as radioactive DNA colony hybridization or plasmid profiling, or the use of clinical assessment techniques such as calcium dependency, serum resistance and autoagglutination. However, these techniques have proven to be impractical for field application. Besides being cumbersome, time consuming and expensive, clinical procedures are often not adaptable to large numbers of cultures and their results are often inconsistent. The colony hybridization technique requires the frequent preparation of the .sup.32 P-labeled DNA probe which is inconvenient and expensive. Further, the colony hybridization technique is potentially hazardous since the method requires the handling of millicurie levels of radioactive material.
Consequently, there exists a need for a method for the evaluation of foods, environmental and clinical samples for the pathogen Y. enterocolitica, which is easy, economical, reliable and safe.